The billboards are popping up all over Beirut: The 3M company is offering to “protect your loved ones” with its line of polyvinyl films designed to keep glass windows from shattering into deadly shrapnel in the event of a bomb blast. And business is booming. A series of suicide bomb attacks over the past five months have turned this carefree capital by the sea into a safety conscious security zone, says Nada Nehme Khoury, 3M Lebanon’s managing director.

Not since the 2006 war with Israel have Beirut residents been so cautious. A widely disseminated U.S. State Department travel alert warning American citizens to avoid “western style” venues has only added to the sense of unease. Even the old downtown souks, that most Arab of outdoor shopping experiences, features brands like Adidas, Zara, H&M and a brand new multiplex cinema. In a city with a reputation for partying during war time—the 2006 World Press Photo of the year summed up local attitudes with a group of young Lebanese blasting past crumpled buildings in a red convertible—the violence is finally taking its toll. The wealthy speak of relocating to Europe or the U.S. A film festival was canceled. Middle class families are staying closer to home, and making them safer. “Usually it’s banks and embassies that install blast film,” says Khoury. “Now it’s families worried about their children.” To Khoury, it’s starting to feel a lot more like 1982, when she established her company three years into Lebanon’s 15-year civil war.

The tit-for-tat bombings that have struck rival religious sects have many fearing Lebanon is headed for a repeat. Not so, says Lebanese analyst Sami Nader, director of the Levant Institute for Strategic Affairs: It’s likely to be much worse. Lebanon is at risk of being subsumed into a far larger and potentially even more devastating sectarian proxy war brewing between Sunni Muslims backed by Saudi Arabia and Shiites backed by rival Iran, one that could rip the entire Middle East apart. That war already has deep roots in Iraq and Syria, says Nader, and Lebanon is next. “Syria, Iraq and Lebanon aren’t three different conflicts, but one war fought on three territories.”

As if to underscore the threat, suspected car bomb attack in the northern Lebanese town of Hermel killed four on Thursday morning and fourteen rockets fired from Syria hit the outskirts of a Lebanese town on Tuesday. The country is also reeling from the influx of Syrian refugees, which are now estimated to make up more than a quarter of the population, straining resources and an already crumbling infrastructure. But it is Lebanon’s internal instabilities that make it so vulnerable to external influence. For ten months, Lebanon’s parliament, largely divided among supporters of a Saudi-backed Sunni party and supporters of the Iranian-backed Shiite group Hizballah, has been unable to form a government. Meanwhile, an international tribunal, convened by the UN at the Lebanese government’s request, is trying four Hizballah members in absentia for their involvement in the 2005 suicide bomb assassination of former Prime Minister Rafik Hariri near The Hague. Hizballah, whose armed militia is said to be stronger than the Lebanese army, has long claimed to Lebanon’s defender against Israel. But if the group is charged with killing a Lebanese leader, it could see an erosion of support. The group’s leadership has dismissed the trial as politically motivated and tensions are high. A specific bomb threat against a Beirut hotel popular with U.N. employees over the weekend may have been linked to the trial, say security officials, but no one knows for sure, adding to the unease.

Hizballah’s growing role in the Syrian war threatens Lebanon even further, says Nader. The group has sent thousands of fighters to help President Bashar Assad in his battle against a wide spectrum of Sunni rebels. Once described by the leadership as a preemptive war designed to keep radical Sunni fighters from advancing on Lebanon, Hizballah’s presence in Syria has incited anti-Shiite militants to attack the group where it is weakest: at home. Hizballah’s Lebanese stronghold, says Nader, “will make Lebanon the center of gravity in the sectarian war.” Radical Sunni groups in Lebanon, once marginalized, have swelled with newly radicalized recruits eager to take on Shiites in Syria. It’s only a matter of time before they bring the war back home. Three car bomb attacks have taken hundreds of lives in the Shiite enclaves south of Beirut since August. On Wednesday, the Abdullah Azzam Brigades, a virulently anti-Shiite al-Qaeda offshoot that claimed responsibility for November’s suicide attack on the Iranian Embassy in Beirut, vowed, via Twitter, to continue its attacks on Iranian and Hezbollah targets in Lebanon.

Syria may have brought long standing regional and sectarian tensions to a boil, but it could also instigate a lasting solution, keeping Lebanon safe from continued spillover, says Nader. Ongoing tensions between Saudi Arabia and Iran, Iran and the United States, and the United States and Russia are the substrate upon which the sectarian proxy war feeds. But the escalating risks of the Syrian conflict may force a recalibration of those toxic relationships. Already the U.S. and Russia have cooperated on a plan to eliminate Syria’s chemical weapons arsenal, and the U.S. and Iran are moving towards an agreement on Iran’s nuclear ambitions. Bridging the vast chasm between Saudi Arabia and Iran will be far more difficult. But as long as they keep fighting, Beirut is likely to keep up its demand for Khoury’s blast film.

Aryn Baker is the Middle East Bureau Chief for TIME, covering politics, society, culture, religion, the arts and the military in the greater Middle East, including Pakistan and Afghanistan. She currently resides in Beirut, Lebanon.